This invention relates generally to high speed anti-friction bearings, and, more particularly, to a novel design of an anti-friction roller bearing cage.
In general, an anti-friction bearing of the roller bearing type finds its greatest utility by being interposed between a stationary and a rotating member or two rotating members in order to substantially reduce the friction therebetween. Such a roller bearing generally comprises an inner ring and an outer ring, with the inner ring being fixedly secured to a rotating shaft. Situated between the inner ring and the outer ring are a plurality of cylindrical rollers. The rollers are generally held in a spaced apart relationship by a separator or retainer, more commonly referred to as a roller cage. As the shaft rotates, the inner ring rotates with respect to the outer ring, with the cage and rollers also rotating. As the speed of the shaft increases, the friction generated by the relative motion between the cage, rollers and rings increases.
The inner or outer ring of the roller bearing has shoulders or guide rails which axially contain therein the rollers in order to limit their degree of skew. The cage or separator which is utilized to separate the rollers reduces the rub velocity that would generally occur between the rollers without a separator or cage in place. It is therefore highly desirable to incorporate a cage within the roller bearing design since lower rub velocities generally result in less roller wear.
In the past conventional cages have been designed with square or rectangular pockets for positioning the rollers. With this type of cage design, roller wobble (skewing) results in impact of the roller and cage at or near the cage pocket corners. If the impact force of the roller against the cage is sufficient to cause cage fracture, a very rapid loss of rolling and/or centering capability of the bearing will result. Wobbling of the roller, also called skewing, is the amount a roller can turn within the constraints of the bearings shouldered ring while the angle of turn is called the roller skew angle.
If a roller bearing starts spalling on the raceways, the rollers will start to jump or bounce around and impact the cage near the corners. Also, if a roller bearing has one or more unstable or unbalanced rollers, the same end result will occur; and the cage will be continually impacted at the corners until the cross rails or side rails of the cage fracture or fall out. Generally the conventional cage design is such that stress concentrations occur near the cage pocket corners as a result of impact from the rollers. This is a major weakness which results in cage fracture of either the cross rails or side rails. Such cage fracture leads to rapid bearing deterioration.
It is therefore abundantly clear that as greater demand is placed upon high speed anti-friction bearings, it would be highly desirable to provide an anti-friction roller bearing which incorporates therein a roller bearing cage which aids in increasing the life expactancy of the anti-friction roller bearing. This can be accomplished if a roller bearing were designed which could provide sufficient time prior to loss of centering of the rollers so that inspection of the bearing could adequately take place.